Questions tagged [grass-gis]
GRASS GIS (Geographic Resources Analysis Support System) is a free, open source geographical information system (GIS) specialized in handling raster, topological vector, image processing, and graphic data. GRASS GIS is a high performance analytical GIS and remote sensing with focus on modularity. Users can process both day-to-day data as well as massive time series.
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Grass GIS vector seem to lost connection to database table, but in file dbln connection exists
After I imported a big vector file and table in sqlite.db was successfully created, there were some operations then I got an error:
DBMI-SQLite driver error:
Error in sqlite3_prepare():
select * from ...
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QGIS Union is slow. How to speed up or which alternative to use, creating the same output?
I have two polygon layers which I want to union. One layer (1) is just one big feature, the other (2) contains 250’000+ features. Layer 1 was created this way: Several polygons --> fix geometry --&...
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How to compare two DEMs and show their difference?
I want to compare my DEMs with each other (ASTER GDEM2 and SRTM4.1). I know, that the GDEM has some "holes" with wrong elevations (I found 3 of them in my working area). Now I need to know, if there ...
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QGIS GRASS Processing Not Working on MacOS?
Recently upgraded to QGIS3 (3.0.2) for MacOS (High Sierra) and encountered GRASS (7.2.2) issues. Tried adding a custom variable and now when running GRASS algorithms (e.g. r.reclass) I get the ...
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Python array based alternative to GRASS r.cost
I am looking for a numpy array based alternative to the GRASS r.cost function.
I have a friction surface raster where the value of each cell corresponds to travel time. I would like to find the cells ...
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Using r.reclass.area.lesser in QGIS?
I want to reclass small areas in QGIS 2.18, but it seems to fail calling the algorithm in GRASS GIS. The interesting lines from the Log of the tool:
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C:\PROGRA~1\QGIS2~1.18\bin>g.region n=...
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How to get centerline of the mask images
I am working on the centerline extraction, I have tried skeletonize, RivGraph and several other methods but could not get a good centerline. First the line on the ends are not following the center and ...
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Can't get GRASS r.water.outlet to work
I'm new to GRASS.
We want to delineate a watershed using the LIDAR data we have our hands on.
I tried to follow several procedures to do so, but despite all my efforts, I can only get it to select a ...
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How create voxel 3d (x,y,z,attribute) in GRASS GIS from CSV file
I have a csv file with (x,y,z,attribute) x,y,z,attribute are float value, and I want to do a voxel 3D in Grass Gis, the documentation and examples are poor, so please I need some help.
I am using ...
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Dealing with no-data values in raster calculator of QGIS
I am trying to patch two rasters with raster calculator but I am not finding the way to work with no-data values.
Lager@1 has some information I need as first option, this has as no-data -9999 (...
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GRASS GIS, r.li modules: How to fix "ERROR: Illegal areas disposition"?
While trying to run commands in examples of GRASS GIS r.li module, I get the error.
This is the output I get from commands in the examples
grass_cmd_output(Language:Japanese)
(Fri Sep 4 13:12:18 2020)...
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GRASS Tools Panel (vers 8.3.1) in QGIS (vers 3.34.4): Filter button does not work
Here is a screenshot of what I am addressing. As you can see if I type any module's name I don't get any result.
How can I fix that?
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Cannot create new mapset in QGIS 3.4.6
I activated the grass 7 plug in, but get the following error:
GRASS intit error: GRASS was not found in 'C:PROGRA~1/QGIS3.4/apps/grass76' (GISBASE), provider ans plugin will not work.
I also cannot ...
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v.generalize along tile edges
I have a problem with v.generalize and I hope I can find help here.
So what I'm trying to do is the following: I have a large number of 1x1 km tiles of rasters that represent traffic areas (roads, ...
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Install QGIS 3.4 with GRASS support in Ubuntu 18.04
I can install QGIS3.X but cannot run a GRASS process. I get the popup:
This algorithm cannot be run :-(
GRASS 7 can't be found on this system from a shell. Please install it or configure your ...
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Can't find d.rast.edit in my GRASS modules
I'm trying to manually edit a raster by using the GRASS tool d.rast.edit as I've seen it's worked for other users. However, even though I have the rest of the GRASS tools, I can't seem to find the ...
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r.out.gdal exports raster with projection but without extents
Exporting raster with r.out.gdal with PCRaster driver gives two files - .map itself and .xml with projection and colormap. But... I can't find the information about extent. Projection is EPSG:4623 (...
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Doing kernel density estimation with physical barrier/ boundary in QGIS [closed]
Does anyone know of a program that will allow kerneling that takes a boundary into account in its calculation rather than simply masking areas that are impossible?
So far I have found:
GME add on for ...
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GRASS v.clean tool in QGIS gives empty output
I am trying to run v.clean in QGIS 3.10.7. I have a 2D LineString dataset saved in GPKG format and I want to run v.clean to clean up some messy topology.
But whenever I run it, I get the same result - ...
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v.clean with rgrass does not work, vector type not found
I'm trying to clean a vector file called network with rgrass library using v.clean. Here's my code:
Sys.setenv("GRASS_INSTALLATION"="C:/Program Files/GRASS GIS 8.3/")
library(...
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How to clip raster in GRASS GIS?
I am using GRASS GIS 7.2.0. The intent is to clip my DEM raster. I have searched available raster tools but didn't found anything allow me to clip my raster using polygon vector or interactively.
How ...
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Calculating peaks in DEM using GRASS
How could I extract all peaks from a DEM (large mountainous area) using GRASS?
Peak means something like: a pixel which is sourrounded by other pixels with smaller elevation numbers in a area ...
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Copying Grass data from one location to another in Grass GIS
I have created several Grass locations with single mapsets while processing a series of satellite imageries at different stages of my analysis.
Now I need to copy some preprocessed rasters and ...
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Finding vector line bearing in QGIS or GRASS
How can one extract the bearings from a set of lines in a vector file?
I'm trying to find the bearings of several straight vector line segments (simplified contour lines, actually) and can't figure ...
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How to fix "No module named grass.script" error in Linux PyCharm?
I'm trying to use v.generalize in the GRASS GIS library within a python code in PyCharm on my Linux Ubuntu system to make a shapefile that originally was a raster look less "blocky" by ...
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DCELL cell type is set automatically for raster after r.resamp.interp
After interpolation with r.resamp.interp with bilinear method DCELL cell type is set for raster. When I export it with r.out.gdal I get a precision loss error, as I export it as Float32 (PCRaster ...
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Input/Output Warning and uncompression error during v.rast.stats processing
First I use command r.slope.aspect elevation=dem slope=dem_slope format=percent --overwrite to calculate slopes in percent.
I get a warning during slope calculation: WARNING: Unable to flush file ...
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Colour intersecting viewsheds by number of intersects
I'm creating a PyQGIS plugin which utilises the Grass7 r.viewshed algorithm. It creates viewsheds as .tif Layers in the project, using the main raster layer as a Digital Terrain/Elevation Model for ...
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Install GRASS GIS extension r.pi including r.pi.prox and implement the Addon in QGIS
I would like to install the GRASS GIS addon r.pi within QGIS,
I only have access to basic GRASS commands
I installed QGIS using the osgeo4w-setup-x86_64.exe advanced installation using the http://...
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Why importing QGIS rasters into GRASS Mapset is not working
I am using GQGIS 3.30. I enabled GRASS and Processing Plugins, and pointed them to the right directory. I created a new mapset and location. Then I used the GRASS toolbox "Import raster into ...
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GRASS r.horizon returns nonsense
I am trying to calculate the horizon profile from a point on a mountainside, through the appropriate DTM elevation file and the GRASS function r.horizon.height (via QGIS).
However, the output looks ...
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QGIS Grass Raster import using r.in.gdal.qgis: 'Layer data source could not be found'
I'm a QGIS learner following the official QGIS Training Manual. I'm on Module 12.1. My problem is that when I try to add a raster layer to GRASS using r.in.gdal.qgis, the resulting layer shows a red ...
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GRASS : r.resamp.rst error : "Not enough disk space--cannot write files"
When I try to use the tool "r.resamp.rst", it gives me as answer:
*r.resamp.rst input=map@PERMANENT ew_res=11 ns_res=11 pcurv=curv
Processing all selected output files will ...
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Why new v.dissolve procedure generates new database tables and causes an error on adding columns later?
The new v.dissolve procedure includes, as the documentation states, two independent processes: v.reclass and v.extract, being a front end to those.
In my case when v.reclass is called it creates a new ...
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GRASS 7.4 addons look installed but not accessable
I'm tring to install the addon v.centerline using the GRASS GUI 'Fetch & install extension from GRASS Addons'. I get the following message saying it's installed yet it doesn't show up. I tried ...
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Different area between Query raster/vector tool and v.to.db
I found a discrepancy between the select GUI tool "Query raster/vector" and v.to.db, and I do not know why. I attached the pictures.
First image (image 1) show that the attribute "...
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Loading and reprojecting .nc file without projection
I am trying to extract some bands from a .nc file. I don't know the file projection (if there is one), thus I created in GRASS GIS a newLocation with no projection (just a XY Cartesian plane) and ...
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Segment lines by given divider
I a trying to segment lines with specific values that are stored in a field. For example, I need my line 1 which is ~84m long, to be segmented into two segment that are 31m and 53m long. I have a ...
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Using v.voronoi.skeleton in Qgis 3.43 with Grass8
In previous QGIS-versions that used Grass7 I designed a model that used v.voronoi.skeleton. But with the upgrade to 3.43, and Grass8, this model will not work anymore. It complaints that grass7:v....
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What is the right way to dissolve vector features in GRASS GIS on attribute values of one column summarizing or averaging others?
The line product of v.overlay contains a column with zones number and a stack of other attributes.
What I want:
Dissolve features (lines) on attribute column that contains zones number. Other ...
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Fatal Error when trying to download addons for GRASS 8.3.1
I get an error with g.extension r.stream.order:
ERROR: Failed to get branch from the Git repository
<https://github.com/OSGeo/grass-addons/>.
fatal: unable to access 'https://...
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How to get zonal statistics of a vector map by areas from another vector map in GRASS GIS?
I have a map with areas (polygons) and another map with lines for example. Lines have multiple attributes and I want some of them to be summed and written to new columns of my areas map. Each polygon ...
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Error installing r.stream extension, GRASS GIS on MacOS
When I attempt to run:
g.extension r.stream.order
I get the following error:
Fetching <r.stream.order> from GRASS GIS Addons repository (be patient)...
Compiling...
clang: warning: no such ...
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How do I calculate albedo in QGIS from a Landsat 8 image downloaded from EarthExplorer
I'm using QGIS and I'm struggling to calculate the albedo from the images. I don't understand how to use GRASS as every time I use it, I get something that doesn't make sense.
Sor far, I have ...
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Using spgrass6 and GIS_LOCK
I have one question about the use of GRASS within R session, i'm able to do some basic task, but i have one important issue is to use GRASS graphics through spgrass6::execGRASS.
I'm aware of the ...
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Installation of QGIS 3.4.4 on Ubuntu 16.04 fails to install qgis-plugin-grass because of uninstallable grass760 dependency
I have used the instructions here marked Tested 29/06/2018 to install QGIS 3.4.4 on Ubuntu 16.04. While QGIS installs nicely I get an error on installing qgis-plugin-grass. Subsequently the Grass ...
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Use v.clean function from GRASS in Jupyter Notebook
I want to automate a process which involves using v.clean tool from GRASS inside a Jupyter Notebook. I've read documentations on how to use Python with GRASS, but it seems impossible to do it or I don'...
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QGIS v3.10 GRASS plugin on MacOS for hydrology
Installed QGIS 3.4 and then 3.10, both gave errors "Grass was not found in /usr/local/opt/osgeo-grass/grass-base" In both cases the directory /usr/local/opt/osgeo-grass/ did not actually exist. I ...
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Problem with v.in.ogr.qgis in QGIS
I received a shapefile containing data from a topographic survey of a farm. The file has a lot of lines containing elevation data. The person who made the survey did it with a GPS set up on a ATV.
...
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GRASS init error
I have installed the GRASS 7.8.7 plugin on QGIS. However, when it loads up the GRASS drop down is available but key functions such as New Mapset etc. are greyed out.
I also get the following error ...
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